how to catch java exception from MATLAB code

Question

when I call myFunction(test) it goes correctly but throws java exception

java.lang.StringIndexOutOfBoundsException: String index out of range: -1

and I would like to catch it and/or catch any java exception.

I tried :

try
  myFunction(test)
catch exp
  mess = exp.message
end

but the mess is empty ... how could I check that myFunction doesn't catch any java exception ?

See example from http://www.mathworks.com/help/matlab/ref/matlab.exception.javaexception-class.html. — Mihai8, Jul 11 '14 at 10:50
but as I said, the mess returns empty whereas it should return the exception — lola, Jul 11 '14 at 10:52

score 0 · Answer 1 · answered Jul 11 '14 at 12:00

0

Either any of below can be use

Instead of "exp" use ME, it is MATLABException Variable which actually catch and store in Message
use "ERROR" instead of "exp" and and then display Message directly on MATLAB command window

answered Jul 11 '14 at 12:00

Konark K

147
8

score 0 · Answer 2 · answered Jul 12 '14 at 00:57

The ability to access Java exceptions from MATLAB was added in R2012b. If I'm not mistaken, prior versions could only catch exceptions in a general manner without specific error information about the Java error.

Example (tested on R2014a):

try
    openStream(java.net.URL('http://non.existant'))
catch ME
end

The exception caught is a MATLAB object that wraps the original Java exception:

>> ME
ME = 
  JavaException with properties:

    ExceptionObject: [1x1 java.net.UnknownHostException]
         identifier: 'MATLAB:Java:GenericException'
            message: 'Java exception occurred: 
java.net.UnknownHostException: non.existant

    at java.net.AbstractPlainSocketImpl.connect(Unk...'
              cause: {}
              stack: [0x1 struct]

so we can access the entire error stack trace:

>> printStackTrace(ME.ExceptionObject)
java.net.UnknownHostException: non.existant
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at sun.net.NetworkClient.doConnect(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.<init>(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at java.net.URL.openStream(Unknown Source)

how to catch java exception from MATLAB code

2 Answers2

Example (tested on R2014a):